class Solution {
public:
    int minNumberOfFrogs(string croakOfFrogs) {
        string t = "croak";
        int n = t.size();
        vector<int> hash(n);

        unordered_map<char,int> index;
        for(int i = 0;i<n;i++){
            index[t[i]] = i;
        }
        for(auto e:croakOfFrogs){
            if(e == 'c'){
                if(hash[n-1] != 0) hash[n-1]--;
                hash[0]++;
            }else{
                int i = index[e];
                if(hash[i-1] == 0) return -1;
                hash[i -1]--;hash[i]++;
            }

        }

        for(int i =0;i<n-1;i++){
            if(hash[i] != 0){
                return -1;
            }
        }

        return hash[n-1];
    }

map <F3> :NERDTreeToggle<CR>
};
